Ken-Ichiro Imura, Mayuko Okamoto, Yukinori Yoshimura, Yositake Takane, Tomi Ohtsuki
The non-trivialness of a topological insulator (TI) is characterized either by a bulk topological invariant or by the existence of a protected metallic surface state. Yet, in realistic samples of finite size this non-trivialness does not necessarily guarantee the gaplessness of the surface state. Depending on the geometry and on the topological indices, a finite-size energy gap of different nature can appear, and correspondingly, exhibits various scaling behaviors of the gap. The spin-to-surface locking provides one of such gap-opening mechanisms, resulting in a power-law scaling of the energy gap. As a noteworthy example, we show that in a prism-shaped sample of TI nanowire a strong topological insulator could be more gapped than a weak topological insulator.
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http://arxiv.org/abs/1208.0654
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